Spacecraft attitude control system is an important element among various systems of a spacecraft. The precision, stability, and reliability of spacecraft attitude control are key technologies during the research process of spacecrafts. In recent years, spacecrafts need to be responsible for more complex tasks and therefore have a continuously increasing demand for electric power. Accordingly, a larger solar panel is needed in order to meet the demand of the tasks. In addition, as spacecrafts need to perform tasks at a longer distance, the requirements on communication antennas also become increasingly higher, and antennas need to be designed to have a structure as large as possible so as to implement data exchange and communication. These requirements result in increasingly larger appendages of the spacecraft. In terms of the launch costs and the technical implementation difficulty, the above appendages such as solar panels and communication antennas generally adopt low-density, low-rigidity flexible structure designs to ensure that tasks can be completed without adding too much weight to the spacecraft system, so as to ensure that the spacecraft can be launched to a predetermined orbit. However, if a large number of flexible appendages are used, attitude control of the spacecraft body will be affected. Because the flexible structures will incur vibration during motion of the spacecraft body, which will affect the accuracy of spacecraft attitude control.
In addition, because flywheels have such advantages as stable output and long service life, almost all long-life, high-precision, and multi-function satellites that were launched in recent years use flywheels as the main execution component. However, the flywheel has a very distinctive feature, that is, limited by processing conditions, a friction moment is generated when the speed of the flywheel is low and crosses zero, affecting the spacecraft attitude control system. Even in some cases, because the rotational speed of the flywheel repeatedly crosses zero, the flywheel chatters, and causes chattering of the spacecraft body with flexible appendages and further causes chattering of the flexible appendages, making it more difficult to stabilize the spacecraft system and implement high-precision attitude control. Therefore, to precisely implement the spacecraft attitude control, the impact of the above two types of interference needs to be overcome in the spacecraft configuring process.
Therefore, there is a need of a method for attitude controlling based on finite time friction estimation for a flexible spacecraft, which can effectively estimate and compensate for friction disturbance.